The cuts affecting the monitoring of self-managed super funds, according to the union, were concentrated in the "superannuation active compliance" sections at Moonee Ponds in Victoria and Parramatta in NSW.

The union said it had been proposed to reduce the workforce of this section from 85 to 60 at Moonee Ponds.

Executive level 1 positions would shrink from 12 to four, APS 6 positions from 17 to four, APS 5 positions from 19 to four and APS 4 positions from 27 to seven. But there would be an increase from 10 to 28 in APS 3 positions.

It is proposed to reduce the superannuation active compliance unit from 114 to 87 positions at Parramatta.

The number of executive level 1 staff would be reduced from 12 to five, APS 6 positions from 27 to seven and APS 5 positions from 28 to 14. An extra 14 APS 3s would be employed.

The ATO will reduce staffing by 4700 by 2017-18. A total of 2100 cuts will come in 2014-15 while another 900 reductions are working their way through the system.

The Australian Services Union said on Thursday ATO staff had been sounded out about working an extra nine minutes a day before entering bargaining on working agreements.

But a former senior public servant warned that lengthening shift times had nothing to do with increasing productivity.

Former Defence Department deputy secretary Paddy Gourley said more hours increased output but had little influence on productivity, which was defined as the unit of output produced for each unit of labour.

In fact, he said, the more hours an employee worked, the less productive they became towards the end of their shift.

Mr Gourley said the federal government's push to link remuneration with productivity in the public sector was fraught with measurement problems.

"For most jobs in the public sector, it's very difficult to measure output," he said.

"If you're writing policy in the Department of the Prime Minister and Cabinet or Treasury, how you measure output is anyone's guess."

He noted that even productivity in call centres could be difficult to measure, simply because some customers were more difficult than others.

"[Linking remuneration with productivity] is wrong-headed and it can have perverse outcomes," Mr Gourley said.

"What bargaining ought to be about is doing what every other sensible employer does – the placing of rates of pay in a reasonably competitive position.

"Staff will be hard-working and productive if they think they're being fairly treated."